The sun’s visible rays are the ones in the colour spectre – from shorter waved indigo rays to red rays with longer wavelengths. Then there are the invisible rays. Those with longer wavelengths than the red ones are infrared rays, and those with shorter wavelengths are ultraviolet (UV) rays.
The invisible ultraviolet sunrays are especially dangerous. They are UVA, UVB and UVC.
UVA: the tanning rays
- are not blocked out by clouds;
- are dangerous thoughout the day;
- penetrate deep into the skin; and
- cause serious damage to the deeper skin layers - even before your skin turns red.
Up to 85% of UVA rays penetrate thick glass and 77% will penetrate a metre of water and wet cotton clothing. The damage to the elastic connective tissue in the deeper layers of the skin makes the skin tough and wrinkled and increases the risk of cancer.
UVA rays also cause cataracts and blindness. Sunbeds and tanning lamps emit UV rays and are unsafe, even though advertisements may claim the contrary. A welding torch also emits dangerous UVA rays.
Not all sunscreens protect you against damage caused by UVA rays.
UVB rays cause redness
- UVB rays cause redness;
- tanning of the skin; and
- they are partially absorbed by the ozone layer.
Up to 35% of UVB rays penetrate thick glass, and 50% will penetrate a metre of water and wet cotton clothing. UVB causes the top layers of your skin to release chemicals that make your blood vessels expand and leak fluid, causing pain, inflammation and redness. This is known as sunburn. This sort of damage can happen within as little as 15 minutes and can continue to develop for up to 72 hours after you’ve been exposed to the sun.
The skin cells damaged by sunburn will die and peel away in flakes or sheets. Peeling is a little unsightly, but it’s actually your body's way of disposing of damaged cells.
UVC rays – luckily absorbed by the ozone layer:
- UVC rays have a shorter wavelength than UVA or UVB and are the most dangerous rays.
- Luckily, most of these rays are still absorbed by the ozone layer. If not, chances are good that everybody will develop skin or even other types of cancer.
- (Health24, updated December 2008)